2 files changed, 3 insertions, 3 deletions
diff --git a/actionmailer/lib/action_mailer/railtie.rb b/actionmailer/lib/action_mailer/railtie.rb
index 215d0199af..a727ed38e9 100644
--- a/actionmailer/lib/action_mailer/railtie.rb
+++ b/actionmailer/lib/action_mailer/railtie.rb
@@ -45,9 +45,9 @@ module ActionMailer
         register_observers(options.delete(:observers))
 
         options.each { |k,v| send("#{k}=", v) }
-
-        ActionDispatch::IntegrationTest.send :include, ActionMailer::TestCase::ClearTestDeliveries
       end
+
+      ActiveSupport.on_load(:action_dispatch_integration_test) { include ActionMailer::TestCase::ClearTestDeliveries }
     end
 
     initializer "action_mailer.compile_config_methods" do
diff --git a/actionmailer/lib/rails/generators/mailer/mailer_generator.rb b/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
index 5a5c9d32bb..ae5757917e 100644
--- a/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
+++ b/actionmailer/lib/rails/generators/mailer/mailer_generator.rb
@@ -15,7 +15,7 @@ module Rails
 
       protected
         def file_name
-          @_file_name ||= super.gsub(/\_mailer/i, '')
+          @_file_name ||= super.gsub(/_mailer/i, '')
         end
     end
   end